1. Field
The invention pertains to composite insulating panel-boards to be used in building construction, and in particular to composite panel-boards comprising a rigid, gypsum board, base panel having a layer of rigid, plastic foam adherant to and covering one of the broad flat surfaces of the gypsum board base panel.
2. State of the Art
Foamed plastic is a good thermal insulator, and has been used extensively in the building industry. Unfortunately, foamed plastic is, under ordinary circumstances, unable to qualify for use in some types of wall and roof constructions. To overcome the problems involving the combustibility and susceptibility to physical damage, sandwich constructions have been produced having a foamed plastic core between dense, incombustible materials such as asbestos cement board, porcelained or enameled steel, aluminum, tempered glass, and perlite board.
Generally, the sandwich constructions have been made by gluing sheets or panels to the broad, flat surfaces of a preformed, foamed slab of plastic using a separate adhesive. In U.S. Pat. No. 3,510,391, a composite insulation board is disclosed wherein a foamed urethane sheet is formed in-situ on the face of a perlite board. Problems associated with these sandwich type constructions include poor dimensional stability, inadequate adhesion between the outer facing and the foam core, and poor surface characteristics of the facer material.
A composite panel has been made by adhesively bonding of a preformed sheet of plastic to a gypsum wallboard. However, all known attempts to form the foamed plastic in-situ on gypsum board have been commercially unsuccessful due to poor adherence of the foam layer on the gypsum board, and also due to non-uniform cell formation in the foam, especially adjacent to the face of the gypsum board. When plastic foam is formed in-situ on gypsum board, large pores are formed adjacent to the face of the gypsum board, and these pores connect to each other to form worm-hole like tunnels extending outwardly from and along the face of they gypsum board.